UMMS scientists seek ways to use powerful gene editing tool to excise latent HIV virus
University of Massachusetts Medical School
9-Apr-2015 WORCESTER, MA - The virus that causes AIDS is an efficient and crafty
. Once HIV inserts its DNA into the genome of its host cells, it has a long incubation period, and
can remain dormant and hidden for years. And while physicians can mix and match a cocktail from
a host of antiretroviral drugs to keep the virus in check, the virus can reactivate if
treatment is stopped.
In an attempt to render latent HIV completely harmless, researchers at the University of Massachusetts
Medical School are using Cas9/CRISPR, a powerful gene editing tool, to develop a novel technology that
can potentially cut the DNA of the latent virus out of an infected cell.
"On the simplest level we're employing a very precise pair of scissors to go in and clip out all,
or part of, the HIV genome and reattached the severed ends of the human genome," said principal
co-investigator Scot Wolfe, PhD, associate professor of molecular, cell and cancer biology at
UMass Medical School. "If we could do that, the hope is that this would be a step on the
road to getting a functional cure for HIV."
A component of the immune system found in normal bacteria, in its natural state CRISPR protects
bacteria from viral invasion. Since its discovery, researchers have been furiously finding ways to
program this system to quickly and selectively edit specific genetic sequences for study.
For all its versatility, applications for the CRISPR system remain confined to the lab. Despite recent
advances showing that Cas9/CRISPR can edit HIV from an infected cell in culture, this technique remains
too imprecise to be used clinically because of its tendency to cut into random regions of the genome,
producing deleterious, off-target effects.
To improve the fidelity and precision of the Cas9/CRISPR gene editing system for this project, Wolfe
has proposed fusing it with an additional domain that improves its specificity. This would conceivably
allow the CRISPR system to edit out only the HIV DNA without the potential for stray cuts in the
human genome.
The other hurdle to using current Cas9/CRISPR technology against HIV is that while researchers have
some notions where the virus might be hiding, they still don't know how to find the virus in latently
infected cells.
"Cells that are infected with HIV are permanent carriers of the viral genome. They are a kind of time
bomb that can reactive at any time if a patient stops taking their antiretroviral treatment," said
principal co-investigator Jeremy Luban, MD, the David J. Freelander Professor in AIDS Research
and professor of molecular medicine at UMass Medical School. "In order to attack the virus in
its latent state, we really need to understand where the virus lives and what it needs to survive."
Drs. Luban and Wolfe will use a combination of innovative technologies to describe and model HIV DNA
integrated into the genome of reservoir cells, also known as provirus. Characterizing the genomic
landscape of these latently infected cells will allow the researchers to identify vulnerable and
accessible genetic sequences that can be potentially cut out of the HIV virus to make it
permanently inactive.
"Many scientists are looking for tools that will activate the virus so it will be visible to the
immune system or drugs. We've chosen a different approach that looks to isolate and excise the
provirus directly from resting cells," said Luban.
With a model of the latently infected cells' genome from which to work, the hope is that Wolfe can
use his precise gene editing tool to excise the latent virus from cells. Part of the project will be
to assess whether the precision of the system has improved enough to allow for selected removal of
the HIV genome in humanized mouse models and cells from infected patients without causing
collateral damage to the human genome.
"The underlying premise of this project that Scot has pushed forward using new technologies that he
has developed, is to genetically engineer a system that can potentially remove the HIV genome from
infected cells," said Luban. "The hope is that one might develop the tools to deliver these
agents to cells of the human immune system and actually eliminate the virus from where it is hiding."
Joining Luban and Wolfe on the five year, $4.6 million, National Institute of Allergy and Infectious
Diseases funded project, are Dale Greiner, PhD, the Dr. Eileen L. Berman and Stanley I. Berman
Foundation Chair in Biomedical Research and professor of molecular medicine; Oliver J Rando
MD, PhD, professor of biochemistry and molecular pharmacology; Job Dekker, PhD, professor
of biochemistry and molecular pharmacology; and Manuel Garber, PhD, director of the
Bioinformatics Core and associate professor of molecular medicine. Each will
lend their respective expertise in developing humanized mouse models;
mapping chromatin structure; modeling 3D chromosome organization; and computational biology.
Additionally, Katherine Luzuriaga, MD, professor of pediatrics and medicine, and
Thomas C Greenough, MD, professor of medicine, will provide clinical expertise on the project.
"We've assembled a team of researchers here at UMass Medical School with the goal of better
understanding the intricate structure of the latent HIV virus when integrated into immune
cells because we believe that will allow us to better target it with CRISPR for gene
editing," Wolfe explained.
About the University of Massachusetts Medical School
The University of Massachusetts Medical School (UMMS), one of five campuses of the University system, comprises the School of Medicine, the Graduate School of Biomedical Sciences, the Graduate School of Nursing, a thriving research enterprise and an innovative public service initiative, Commonwealth Medicine. Its mission is to advance the health of the people of the commonwealth through pioneering education, research, public
service and health care delivery with its clinical partner, UMass Memorial Health Care. In doing so, it has built a reputation as a world-class research institution and as a leader in primary care education. The Medical School attracts more than $240 million annually in research funding, placing it among the top 50 medical schools in the nation. In 2006, UMMS's Craig C. Mello, PhD, Howard Hughes Medical Institute Investigator
and the Blais University Chair in Molecular Medicine, was awarded the Nobel Prize in Physiology or Medicine, along with colleague Andrew Z. Fire, PhD, of Stanford University, for their discoveries related to RNA interference (RNAi). The 2013 opening of the Albert Sherman Center ushered in a new era of biomedical research and education on campus. Designed to maximize collaboration across fields, the Sherman Center is home
to scientists pursuing novel research in emerging scientific fields with the goal of translating new discoveries into innovative therapies for human diseases.
